Scientists have found hawksbill turtles "hiding" in mangrove forests of the eastern Pacific.

The team, that has been tracking the turtles for three years, also found that the critically endangered animals nested in these estuaries.

The discovery of this previously unknown sea turtle habitat was published recently in the Royal Society journal Biology Letters.

It could explain why the species went undetected in the region for so long.

Mangrove forests, which are unique coastal tree and shrub habitats, are also under threat. They could represent an important breeding and nesting site for the species, which was thought to depend on coral reefs.

Alexander Gaos, a conservation scientist with San Diego State University and the Eastern Pacific Hawksbill Initiative, led the research.

He and his colleagues tracked hawksbills in four countries - El Salvador, Honduras, Nicaragua and Ecuador - using satellite tracking tags glued to the turtles' backs.

Dr Gaos said that the turtles might be spending their entire lives in these "cryptic habitats".

"Couple that with the fact that there are very few individuals left - hawksbills in the eastern Pacific are one of the world's most endangered sea turtle populations - and it's no wonder researchers didn't know about them!"

The scientists worked with local fishermen and even illegal egg collectors, in order to find hawksbill turtles to fit their tags to.

They hope their revelations about the species' habitat will inform conservation efforts.

Why the turtles were "seeking shelter" in mangroves was not clear.

The scientists think it might be a recent adaptation brought on by a lack of their more typical habitat of coral reefs in the region.

Dr Gaos said: " We now have a better idea of where to look for them, which may help us direct research and conservation of the species, upon which their survival may ultimately depend."

The one-metre emperor penguin is being prepared to leave Wellington on a more-than 3000km journey back to Antarctica at the end of this month.

The penguin, nicknamed Happy Feet, has made headlines since he washed up on the Kapiti Coast's Peka Peka Beach in June.

The nation has watched while he recovered after operations at the Wellington Zoo to wash sand, rocks and liquid from his stomach.

Happy Feet will catch a ride on the National Institute of Water and Atmospheric Research's (Niwa) largest research vessel on August 29.

After four days of travelling on the Tangaroa, the 26.6kg bird will be released into the ocean at a point east of Campbell Island.

The drop-off location is within the natural range of young emperor penguins.

Niwa was looking at two ways of getting Happy Feet off the ship, said the institute's general manager research Rob Murdoch.

"It depends on the sea conditions. One of the options is to have a slide at the stern of the ship so he can, under his own steam and time, slide down into the water."

The second option was to lower the penguin into the ocean in a workboat, from which a staff member would help get him back into the water.

Happy Feet will be travelling in style while on the boat. A Wellington Zoo team was developing a refrigerated crate that would keep the penguin cold enough, comfortable and safe during turbulent weather said zoo spokeswoman Kate Baker.

He has been living in a zoo enclosure kept refrigerated at temperatures between 0.5 and 2C.

He will be accompanied by Wellington Zoo veterinary manager Dr Lisa Argilla and two Niwa staff.

The Tangaroa was going to Campbell Island to make a month-long fisheries survey on southern blue whiting, so it was a good match-up of resources Ms Baker said.

Happy Feet has been preparing for his release by taking a few dips into a chilled saltwater pool next to his enclosure, said Ms Baker.

She said she expected Happy Feet to make the journey safely.

"Emperor penguins are used to going long periods of time without exercising."

Fans of Happy Feet can track his progress in the wild.

The penguin will be carrying a GPS tracker so his progress can be followed on the Sirtrack website and the Our Far South website.

Said Ms Baker: "It's been really amazing having him here, but it's going to be really good when he goes because it means we've done our job."

SAN JOSE (AFP) – A new species of large land crab was discovered on Cocos Island in Costa Rica, a local newspaper reported on Monday.

University researchers from Costa Rica and the United States discovered the new species, named "Johngarthia cocoensis," on the Pacific Ocean island. The distinguishing characteristic of J. cocoensis, according to the researchers, is its large size--a male can measure 40 cm (15.7 inches) with their front legs extended (females measure smaller).

The crabs live in holes dug into the soil and eat primarily grasses and seeds.

Robert Perger and Rita Vargas from the University of Costa Rica and Adam Wall from the Los Angeles County Natural History Museum are credited with discovering the new species.

Perger told the local newspaper that J. cocensis resembles the J. malpilensis crab, which lives on nearby islands.

"The similarity with other species in the western Pacific indicates that larvae (which develop in the sea) may have crossed to Cocos Island by sea currents," and then adapted to the habitat to grow into a new species he said.

Cocos Island is located off the coast of Colombia but within the territorial waters of Costa Rica and is the only island in the Western Pacific that has a humid tropical forest climate and a wide variety of animal species.

April 28 marks the official opening of the 20th edition of the International Sand Sculpture Festival in Scheveningen (April 29 - June 27).

Seven specialised carvers from the World Sand Sculpting Academy are depicting endangered animal species using more than 300 tonnes of special sculpturing sand.

This year's theme is "Save Our Planet" and visitors can donate one euro by sending a text message to WWF to support the fundraising campaign "Verdubbel Natuur".

The Sand Sculpture Festival in Scheveningen began in 1991 as the first European sand works festival and today, is the longest-running sand sculpture festival in the world attracting hundreds of thousands of visitors each year.

A leopard of a critically endangered species was filmed for the first time in Northeast China's Jilin province, local authorities said Monday.

Cameras on the Sino-Russia border captured a roaming Far Eastern leopard in Hunchun city on April 13, said Yu Changchun, head of the environment protection bureau under Jilin's forestry department.

Soldier Li Mingquan saw the leopard through the surveillance cameras at 3:31 pm.

Animal carcasses, which could have been left by the leopard, were found near the spot one day later, Yu said.

The Far Eastern leopard, also known as Amur leopard or Manchurian leopard, faces an extremely high risk of extinction in the wild, according to the International Union for the Conservation of Nature.

Experts say there are less than 50 Far Eastern leopards in the wild. The feline predators are native to the forests in northeast China, Russia's Far East and the Democratic People's Republic of Korea (DPRK).

About two to four Far Eastern leopards live in the forest of about 100,000 hectares in Hunchun. The number may change as some leopards sometimes cross the Sino-Russia border, said Lang Jianmin, head of the Promotion and Education Center for Hunchun Manchurian Tiger National Nature Reserve.

Dolphin reportedly 'perked up' once being placed back in the Pacific Ocean by rescuers.

A baby dolphin has been rescued in Japan after being dumped in a rice field by a giant tsunami that hit the coast on March 11.

The dolphin was spotted in the flooded field, about 2 kilometers (a mile) from the coast, said Ryo Taira, a pet shop owner who has been rescuing animals abandoned after the 9.0-magnitude quake and tsunami left 23,000 people dead or missing.

"A man passing by said he had found the dolphin in the rice paddy and that we had to do something to save it," the 32-year-old Taira told Reuters.

Taira found the dolphin struggling in the shallow seawater on Tuesday and after failing to net it, waded in to the field, which had yet to be sown with rice, to cradle the 1.2-meter (4-foot) animal in his arms.

"It was pretty weak by then, which was probably the only reason we could catch it," he said.

Taira and some friends wrapped the dolphin in wet towels and drove it back to the sea, where they set it free. The dolphin appeared to perk up when it was back in the Pacific, he said.

"I don't know if it will live, but it's certainly a lot better than dying in a rice paddy," Taira told the Asahi Shimbun newspaper.

(Reporting by Elaine Lies; Editing by Robert Birsel and Sanjeev Miglani)

A mob of about 300-400 villagers poured petrol on a caged leopard and burnt it alive on the outskirts of the Corbett National Park here, even as wildlife wardens and some policemen stood by helplessly, an official said.

The animal was captured alive in Dhandhar village, on the outskirts of the Corbett Tiger Reserve.

According to Uttarakhand Chief Wildlife Conservator S.K. Chandola: ‘Irate villagers (Wednesday evening) forcibly took custody of the leopard that was captured and put in a cage and was being taken away by department officials.’

He said, ‘The villagers doused the leopard with petrol and threw a lit matchstick inside the cage, sending the animal up in flames.’

Chandola said, ‘Even though there were about 35 wildlife officials and four policemen, they were overpowered by a mob of 300-400 people who would not let the officials go anywhere close to the burning animal that kept wailing and roaring inside the cage until he met his end.’

Contrary to some reports, which said the animal had killed a few people over the past few days, Chandola clarified: ‘The leopard had apparently strayed from the periphery of Corbett reserve area and was reported to have attacked and wounded three people on Wednesday.’

Wildlife enthusiasts blamed wildlife officials for not ensuring protection to the leopard which is listed among the endangered species and its killing entails imprisonment up to seven years.

While an FIR had been registered against an unnamed mob, no one has been arrested so far.

Older animals make the best leaders, suggest studies on primates, whales and now elephants.

Advanced age can improve an individual's ability to detect threats, the research found, benefiting others if that individual is a leader.

"The findings highlight the importance of older individuals in natural populations -- not only in elephants, but most likely also in other large-brained, long-lived social species, such as whales and primates, where knowledge can be accumulated over time," said Karen McComb, lead author of the study, appearing in the latest Proceedings of the Royal Society B.

McComb, a behavioral ecologist specializing in psychology at the University of Sussex, and colleagues conducted their experiments on 1500 African elephants living within 58 distinct family groups at Amboseli National Park in Kenya.

Using loudspeakers mounted on a fieldwork vehicle, the researchers played recorded male and female lion roars in the elephants' vicinity. During some experiments, the researchers would play the sounds of three lions roaring at once. Other than humans, lions are the main natural predators of elephants, with powerful male lions being more active hunters. Male lions are, on average, 50 percent larger than female lions.

While all of the elephants reacted more strongly to the sound of three lions, groups led by older matriarchs showed the greatest sensitivity to the more serious threat posed by male lions. These older female leaders, 60 years plus in age, not only listened intently, but they also rallied their group members into defensive maneuvers known as bunching and mobbing where the elephants act like a giant battering ram by charging the lion and harassing it.

"Our work emphasizes the importance of the knowledge that older individuals may possess, which can ultimately lead to benefits for individuals in groups that have older leaders," co-author Graeme Shannon of the University of Sussex told Discovery News.

The research highlights the value of older individuals in elephants-- and past work has suggested the same is true in humans. As Shannon points out, prior research on humans has found that "reasoning about social conflicts improves with age despite declines in many forms of cognitive processing."

Human societies in modern times often tend to revere youth culture. Throughout history and even now, however, "older individuals often emerge as leaders in tasks requiring specialized knowledge," the researchers point out.

The pattern appears to hold true for many other species, such as sperm whales, killer whales, broad-winged hawks, ravens and more.

Peter Tyack, a senior scientist in the biology division at Woods Hole Oceanographic Institution, said he wasn't "surprised by the finding that older female elephants are better able to lead their groups. Their increased knowledge, gained over decades, allows them to make better decisions that provide great benefits to their groups."

Joshua Plotnik, an Emory University researcher and elephant expert, pointed out that although the older individuals are not necessarily alpha, their experience and influence often plays a very important role in the social decision-making process.

United States now biggest market for lion hunting trophies, wildlife coalition warns

American hunters are emerging as a strong and growing threat to the survival of African lions, with demand for trophy rugs and necklaces driving the animals towards extinction, a coalition of wildlife organisations has said.

Demand for hunting trophies, such as lion skin rugs, and a thriving trade in animal parts in the US and across the globe have raised the threat levels for African lions, which are already under assault because of conflicts with local villagers and shrinking habitat.

"The African lion is a species in crisis," said Jeff Flocken of the International Fund for Animal Welfare. "The king of the jungle is heading toward extinction, and yet Americans continue to kill lions for sport."

Two-thirds of the lions hunted for sport were brought to America over the last 10 years, a report released by the coalition said.

The organisations, which include IFAW, the Humane Society of the United States, Humane Society International, Born Free and Defenders of Wildlife, called on the White House to ban the import of lion trophies and parts by listing the animals as endangered species.

The number of wild African lions has fallen sharply in the last 100 years, the organisations said. A century ago, as many as 200,000 roamed across Africa. Now, by some estimates, fewer than 40,000 remain in the wild; others put the figure for survivors at 23,000, and they have vanished from 80% of the areas where they once roamed.

Lions have become extinct in 26 countries. Only seven countries – Botswana, Ethiopia, Kenya, South Africa, Tanzania, Zambia and Zimbabwe – are believed to contain more than 1,000 lions each, according to the Panthera conservation group – which is not part of the coalition making the appeal.

The single biggest threat by far to the animals' survival is humans, though not necessarily western hunters. "It is just the very, very widespread killing of lions, mostly in a conflict situation, by anyone who is trying to farm livestock in Africa and finds it very difficult to co-exist with lions," said Luke Hunter, the executive vice-president of Panthera.

There is also a lot of pressure on lion habitats with wilderness areas shrinking to build roads – such as the controversial highway across the Serengeti – or to make room for agriculture.

But the report by the wildlife coalition, filed with the White House on Tuesday, said western hunters were a growing danger to the lions' survival.

Between 1999 and 2008, 64% of the 5,663 lions that were killed in the African wild for sport ended up being shipped to America, it said. It also said the numbers had risen sharply in those 10 years, with more than twice as many lions taken as trophies by US hunters in 2008 than in 1999. In addition to personal trophies, Americans are also the world's biggest buyers of lion carcasses and body parts, including claws, skulls, bones and penises. In the same years, the US imported 63% of the 2,715 lion specimens put up for sale.

For some countries, including Tanzania, Zambia, Namibia and Mozambique, hunting for sport was the main threat to the lions' existence. But even in countries which did not attract large numbers of tourists on hunting trips, the practice was taking a growing toll.

The conservationists noted that hunters' penchant for bagging a male lion risked wiping out entire prides. The loss of the alpha male could set off a struggle for supremacy among the survivors that could lead to further deaths of adult male lions, or male cubs seen as potential threats.

A hunting ban, the conservationists said, would reduce that threat by taking Americans out of the game. It's one of a range of threats to the survival of the species, said Teresa Telecky, director of wildlife for Humane Society International. "But what is most certainly true is that of all the threats to the African lion, the one we can best address here in this country is their import."

Flocken noted that all of the other big cats are protected – jaguars, leopards and tigers. "African lions are the only ones left out there," he said.

However, other wildlife experts argued that a total hunting ban was a "nuclear option". They said responsible hunting could in some cases help conserve populations by maintaining wilderness areas. Existing US and international regulations, such as the Cites conventions against trafficking in endangered species, could also be reinforced to protect lions, they said.

"If you remove hunting, the very real risk is that you force African governments to generate revenue from that land and the obvious thing is cattle and crops which just wipe out habitats," said Hunter.

Six dolphins have now been seen mastering the technique - furiously paddling their tail fluke, forcing their body out and across the water.

The dolphins seem to walk on water for fun, as it has no other obvious benefit, say scientists working for the Whale and Dolphin Conservation Society.

That makes the behaviour a rare example of animals "culturally transmitting" a playful rather than foraging behaviour.

Only a few species are known to create their own culture - defined as the sharing or transmitting of specific novel behaviours or traditions between a community of animals.

Rare trick

The discovery was made by Whale and Dolphin Conservation Society (WDCS) scientist Dr Mike Bossley, who has spent 24 years studying dolphins living in the Port River in Adelaide, Australia.

In past years, Dr Bossley has witnessed two wild adult female dolphins, named Billie and Wave for research purposes, attempting to walk on water.

Now four other dolphins, including yougn infants, have been recorded trying to learn the trick from the two adults, and have been seen practising, less successfully, in the river.The behaviour, when a dolphin beats its tail fluke repeatedly, so it lifts its body vertically out of the water and then along the surface, is more commonly seen among captive dolphins trained to perform tricks.

In the wild it is extremely rare.

According to the WDCS, apart from Billie and Wave, only one other adult dolphin had previously been seen tail-walking in the Port River during thousands of hours of scientific observations, and then only once.

Billie is thought to have learned the trick during a brief period when she was held captive in a dolphinarium, before being released back into the wild.

She passed the behaviour onto Wave, and now Billie and Wave appear to be passing on their knowledge of how to tail-walk to their wider community.

Other dolphin called Bianca, and her calf Hope, and another calf called Bubbles are also attempting the trick.

These dolphins are now being seen trying to tail-walk many times each day.A number of animals are known to culturally transmit novel behaviours to others of their species.

Chimps learn to fish for termites with sticks, and orcas learn various techniques to hunt seals, for instance.

But few examples have been documented of animals culturally passing on behaviours that are unrelated to obtaining food.

Tail-walking appears to have no function other than play, says Dr Bossley."As far as we are aware, tail-walking has no practical function and is performed just for fun, akin to human dancing or gymnastics," he says.

"Culture in the wider sense of the term, defined as 'learned behaviour characteristic of a community' is now frequently on show in the Port River."

Leopards' spots and tigers' stripes are a camouflage closely tied to their habitats, researchers say.

A UK team examined the flank markings of 37 species of wild cats in a bid to understand the spectacular variety of their colour patterns.

The scientists say that cats living in the trees and active at low light levels are the most likely to have complex and irregular patterns.

They published the findings in a Royal Society journal.

It is not the first study to suggest that wild cats need spots to "vanish" in dense forests, sandy deserts or snowy mountains.

But this time, the researchers analysed the colour patterns' detailed shapes and complexities, stating that these two factors are vital for camouflage.

To examine different patterns, the team used images obtained from the internet and classified them with the help of mathematical formulas.

"[Some species] are particularly irregularly and complexly spotted," William Allen from the University of Bristol, the lead author of the study, told BBC News.

"The pattern depends on the habitat and also on how the species uses its habitat - if it uses it at night time or if it lives in the trees rather than on the ground, the pattern is especially irregularly spotted or complexly spotted."

Dr Allen said that the title has been inspired by a short story of Rudyard Kipling with a similar name, "How the leopard got his spots".

In the story, an Ethiopian first changed his skin colour to black and then "put his five fingers close together (there was plenty of black left on his new skin still) and pressed them all over the Leopard, and wherever the five fingers touched they left five little black marks, all close together. Sometimes the fingers slipped and the marks got a little blurred; but if you look closely at any Leopard now you will see that there are always five spots - off five black finger-tips".

Dr Allen explained that though the fingertips idea was understandably fictitious, Mr Kipling's deduction about leopards needing spotty coats to "disappear" among trees was spot on.

"The mechanism - the fingerprint - isn't the right idea, but it is actually the case that leopard's spots and similar patterns evolve in forest habitats," said the scientist.

Dr Allen's study still fails to explain the mechanism of wild cats' pattern development - but the scientists managed to find a set of numbers to measure the irregularity or complexity of a pattern and correlate this with where the species lives to explain its behaviour.

"We've shown that the usefulness of patterns for species' survival can be related to a mathematical model of how the pattern arises and what that does is it gives more complex information on why the leopard has its spots," said Dr Allen.

And it is all about genetics, he added.

"When you place cat patterning over the evolutionary tree of cats, you can see that patterning emerges and disappears very frequently within the cat family, which is kind of interesting - it suggests that perhaps particular genetic mechanisms can solve very different appearances of cats."

Other theories

Previously, researchers believed that wild cats used their colour patterns to attract members of the opposite sex, but Dr Allen's team discounted this theory, saying that if there were a sexual motive, "you'd expect to see different patterns in males and females, which you don't".

"Another idea is that the patterns might have some sort of social signalling function, but again we didn't support this because the type of pattern cats have isn't related to their social system.

"For example, lions don't have particular flank markings that help them get along with living in prides."

The characteristic koalas, kangaroos, possums and wombats of Australia share a common American ancestor, according to genetic research from Germany.

A University of Muenster team drew up a marsupial family tree based on DNA.

Writing in the Public Library of Science (PLoS) Biology journal, they suggest a single marsupial species moved from the Americas to Australia.

Marsupials differ from other mammals in that mothers carry their young in a pouch after birth.

As well as the familiar Australian species, the family includes the opossums and shrew opossums of North and South America, and also has a presence in Asian countries including Indonesia and Papua New Guinea.

"I think this is pretty strong evidence now for the hypothesis of a single migration [to Australia] and a common ancestor," said Juergen Schmitz, one of the research team.

Tracing relatives

The research was made possible by the recent sequencing of genomes from two marsupials - the gray short-tailed opossum (Monodelphis domestica) from South America, and the Australian tammar wallaby (Macropus eugenii).

The Muenster researchers looked for DNA elements called retroposons.

These are fragments that have been copied and inserted back into DNA in a random fashion at some point during the animal's evolutionary history.

They are among the "jumping genes" that can scatter genetic information along the genome.

If two species carry the same retroposon but a third does not, that indicates that the first two are more closely related to each other than they are to the third.

Sometimes one retroposon is inserted in the middle of another, again giving vital clues as to the sequence of events in a family's evolution.

Using this method, they showed that the American opossums separated from the main lineage first.

Then at some stage an ancestral species migrated to Australia and gave rise to the various families found there now.

When exactly this happened is still unknown, as this kind of analysis does not show when in evolutionary time the retroposons were inserted.

"Maybe it's around 30-40 million years ago, but we cannot say because jumping genes do not give this information," Dr Schmitz told BBC News.

"It's now up to other people, maybe from the palaeontology field, to find out when exactly it happened."

The overall marsupial history is virtually a circular migration.

The earliest identified species (Sinodelphys szalayi) is known from 125-million-year-old fossils found in China.

Subsequently the family - or perhaps a single species - moved across the super-continent of Gondwana into what is now South America.

The marsupial family began expanding about 70-80 million years ago.

After crossing into Australia, they penetrated north into the Indonesian archipelago - almost returning to their Chinese homeland.

The Asian Rhino Foundation was founded in April 2006 by Maaike Leenen and Jeroen Rijnierse, students of Wageningen University in the Netherlands. No other organization in the Netherlands, or elsewhere on the European mainland, had a foundation focusing on the Asian rhino species and the local community.

Images of oil-covered birds are among the most vivid symbols of the wildlife damage wrought by the Deepwater Horizon spill. The brown pelican, which graces the Louisiana state flag and was just brought back from the brink of extinction last year, has been hit especially hard.

Once brought to Fort Jackson, the birds are treated for dehydration and are fed before the difficult clean-up operation begins. They are first bathed in warm vegetable oil, followed by a scrubbing in dishwashing liquid. The birds are closely monitored by veternarians like the U.S. Fish and Wildlife's Sharon Taylor, who release recovered birds back into the wild.

Taylor told the NewsHour during a recent reporting trip that the number of birds rescued is "small compared to the number of animals that are directly impacted -- that we were either never able to find because they were lost out at sea, or that scavengers got onshore, so it's a small percentage of the numbers actually impacted by the oil spill."

Cane toads, one of the world's most destructive invasive species, have started killing native wildlife outside of Australia.

Cane toads are poisonous, secreting a toxin that kills predators not adapted to eat them, and as a result the toads have caused a decline in native Australian reptiles and marsupials.

Now scientists have discovered that the toads are also killing boa snakes in the West Indies, suggesting that other predators in the Caribbean and elsewhere may also be at risk.

The cane toad is a large toad species, which secretes a powerful bufogenin toxin.

Its native range extends from northern South America through Central America and into the southern United States.

In the early to mid 19th Century, the toad was intentionally introduced to islands in the Caribbean, including Jamaica in 1844, and then through the South Pacific.

The toad was introduced to eat and control pests of sugar cane, including rats and beetles.

However, the toad has had a destructive impact in many places where it has spread, out-competing native species.

More recently, the toad has devastated populations of amphibian predators, including large lizards, snakes and marsupials, in Australia.

The threat there continues to grow as the toads spread west across the country from Queensland into New South Wales and the Northern Territory.

Cane toads are so prevalent in Australia that people in the Australian state of Queensland have even taken part in a mass capture of the poisonous amphibians, as part of a collective effort at pest control.

Threat widens

Now scientists have documented the cane toad killing rare native fauna in the Carribean.

Dr Byron Wilson, at the University of West Indies in Jamaica, and his colleagues there and in the US have found numerous examples of cane toads poisoning Jamaican boas (Epicrates subflavus), large predatory snakes that are endemic to the island of Jamaica.

The boa, also known as the yellow snake, is Jamaica's top native terrestrial predator.

Already rare, the snake is threatened by habitat destruction and introduced dogs and pigs.

"To our knowledge, this is the first report of cane toads causing mortality in naturally occurring predators outside of Australia," say the authors in the journal Biological Invasions.

"Although cane toads have been present on Jamaica for more than 160 years, it is clear from our observations that Jamaican boas have not yet learnt to avoid this toxic prey species."

The researchers now fear that the toads could pose a threat to the snake across its island range.

They also worry that other species in Jamaica and on other Caribbean islands are at risk from bufotoxin poisoning.

Humpback whales form lasting bonds, the first baleen whales known to do so.

Individual female humpbacks reunite each summer to feed and swim alongside one another in the Gulf of St Lawrence, off Canada, scientists have found.

Toothed whales, such as sperm whales, associate with one another, but larger baleen whales, which filter their food, have been thought less social.

The finding raises the possibility that commercial whaling may have broken apart social groups of whales.

Friends reunited

Details of the discovery are published in the journal Behavioral Ecology and Sociobiology.

Dr Christian Ramp and colleagues of the Mingan Island Cetacean Study group based in St Lambert, Canada have been studying whales in the Gulf of St Lawrence since 1997.

Together with researchers from Germany and Sweden, the scientists are recording the movements of baleen whales including blue, fin, minke and humpback whales, adding to a set of data that stretches back 30 years.

Baleen whales, which are the largest of all whales, possess huge baleen plates in their mouths, which they use to filter out small prey such as krill and plankton from the water.

Using photographic identification techniques, the researchers can spot which individual whales appear from one year to the next.

During this study, they have found that the same humpback whales reunite each year.

Having spent the rest of the year apart migrating and breeding, individual humpbacks somehow find each other again in the open ocean each summer, spending the season feeding together.

The longest recorded friendships lasted six years, and always occurred between similar-aged females, and never between females and males.

"I was very surprised by the prolonged duration," Dr Ramp told the BBC.

"I was expecting stable associations within one season, not beyond. I was particularly surprised by the fact that only females form these bonds, especially females of similar age."

Underwater enigma

The discovery has puzzled the researchers who made it.

"In toothed whales, you find strong bonds in killer whales, between entire families, and sperm whales between females and juveniles. They basically stay together all their life. There are also strong associations in bottlenose dolphins," Dr Ramp adds.

But "as far as we know, baleen whales are regarded as less social than toothed whales."

There is some evidence that humpbacks in Alaska form stable groups to feed on herring, and female right whales are thought to be more gregarious than males.

However, until now, baleen whales have not been known to reestablish bonds between individuals from one year to the next.

Forming such friendships clearly benefited the female humpbacks, as those that had the most stable and long-lasting associations gave birth to the most calves.

Dr Ramp and his colleagues suspect that the whales form bonds to improve their feeding efficiency each year.

"Staying together for a prolonged period of time requires a constant effort. That means that they feed together, but likely also rest together. So an individual is adapting its behaviour to another one."

How the whales find each other each summer is also an enigma.

"It's an excellent question and I would like to know the answer," says Dr Ramp.

"Where do they meet, and how do they recognise each other?"

He suspects the whales use sound to find and recognise other individuals.

Whaling wipe out

So far, studies on blue and fin whales suggest that these species do not form such friendships.

But the discovery that humpbacks do might have further implications.

Dr Ramp speculates that humpback whales associating with one another may have made it easier for them to be caught in the past by commercial whalers.

As yet, there is no evidence to support this. But if that did occur, it would also mean that whaling may have removed social groups of humpbacks, and their preference to form friendships with other whales.

"Maybe the social traits are re-evolving due to rebounding populations, or they are completely different to the ones before, due to changes in the environment."

Saltwater crocodiles enjoy catching a wave and can travel hundreds of kilometres by "surfing" on ocean currents, a study suggests. Australian researchers used sonar sensors and satellite transmitters to monitor 20 reptiles' movements.

They found the crocodiles undertook numerous trips of over 10km (6.2 miles), but only when a current flowed in their direction of travel.

The results of the research appear in the Journal of Animal Ecology.

The TV personality Steve Irwin, who was nicknamed The Crocodile Hunter, but died in 2006, took part in the study.

Estuarine or saltwater crocodiles are the world's largest reptiles and can grow up to 5.5m in length.

They are poor swimmers and mainly live in salt water - but their "home" spans over thousands of kilometres of the south-east Pacific.

Researchers have long been puzzled by how crocodiles managed to spread themselves so widely.

"Of all the amazing things animals can do, the ability of certain species to migrate significant distances across formidable geographical barriers is one of the most remarkable," write the authors of the recent study.

Although the crocodiles spend most of their life in salt water, they are not considered marine animals as they rely on land for food and water.

The open sea

During the research, a team led by Dr Hamish Campbell, from the University of Queensland, captured 20 crocodiles living in the North Kennedy tidal river in Queensland, northern Australia, and tagged them with satellite transmitters.

They found that during the period of study, eight of them ventured out into the open ocean. One travelled from the river mouth all the way to the west coast of the Cape York Peninsula, in Queensland's far north. That amounts to a total of 590km covered over 25 days.

To do that, the ocean-trotter hitched a ride on a current within the Gulf of Carpentaria (that separates Cape York from Arnhem Land, to the west). This current occurs seasonally, during the summer monsoon.

"[These crocodiles] can survive for long periods in saltwater without eating or drinking, so by only travelling when surface currents are favourable, they would be able to move long distances by sea," commented Dr Campbell.

It took another adventurer - a 4.84m-long male - just 20 days to go more than 411km from from the east coast of Australia's Cape York Peninsula through the Torres Strait (which divides Australia from New Guinea) to the Wenlock River on the west coast of Cape York.

When the crocodile arrived in the Torres Strait, strong currents were flowing in the opposite direction to where it was headed.

So the animal waited in a sheltered bay for four days and continued its trip when the currents changed direction.

Important clues

The scientists also tagged 27 crocodiles with sonar transmitters and spent a year tracking their every move inside the North Kennedy River with underwater receivers.

They found that both male and female crocodiles regularly travelled more than 50km from home, swimming to the river mouth and back.

But the team discovered that crocodiles would only set out on a long journey within an hour of the tide changing. This allowed them to "catch a wave".

They put their trips on hold when the tides reversed, moving out of the river and on to the banks.

Dr Campbell said that the results of the study gave important clues to understanding the evolution of the world's largest reptiles.

"This not only helps to explains how estuarine crocodiles move between oceanic islands, but also contributes to the theory that crocodilians have crossed major marine barriers during their evolutionary past," he said.